The objective of this study is to understand the mechanism of mitosis in Drosophila, an ideal organism for studying mitosis, both because of its genetics and because of the accessibility of different tissues to cytological examination. Mutations induced by PM hybrid dysgenesis in the scabrous (scb), gene, render the diploid nuclei of Drosophila unable to accurately segregate their chromatids. The failure appears to occur at anahase. However, the extant alleles are probably leaky. This study proposes to clone the scabrous gene by P transposon-tagging, to study its expression in diploid and polytene tissues, to clone the coding region into an expression vector and raise polyclonal and monoclonal antibodies that recognizes the scabrous+ protein. The antibody will be used to determine the tissue location of scabrous, and its intracellular location, to test whether it is intimately associated with the mitotic apparatus. Scabrous function will be examined in several ways. The effect of leaky scabrous mutants on meiotic division will be assessed. The antibody will be microinjected into early cleavage embryos to possibly interfere with functioning of scabrous protein during mitosis. We shall isolate other alleles of scabrous, including nulls and temperature sensitive alleles, to generate an alleleic series of phenotype. The more severe alleles will permit an assessment of scabrous function in nondividing cells, such as polytene tissues. In vitro altered scabrous genes will be constructed and introduced by P transformation into files. These constructs will help define noncoding control regions of the gene. The construction of a conditional dominant antimorph of scabrous will also be attempted. This if successful can be used to select new alleles in scabrous as well as other genes whose products interact with scabrous. And other genes involved in mitosis will be identified by P transposon mutagenesis, and their molecular characterization initiated.